Many internal combustion engines are provided with fans or blowers that force cooling air over certain engine surfaces during engine operation. Air-cooled engines typically include engine cylinders and cylinder heads that incorporate heat sinks in the form of cooling fins. In this regard, fans and blowers are often provided to force air over the cooling fins, thereby cooling the engine. To further enhance the circulation of cooling air, and to thereby improve the engine cooling process, many engines include special housings and/or ductwork that guide the cooling air to different areas of the engine that require cooling.
The fans also can provide air to the engine for use in the combustion reaction in the cylinders. Air is drawn through a filter to remove debris from the air stream before the air enters the combustion chamber. For engines operating in environments having significant amounts of airborne dust and particulate debris, screens and the like are often provided in an attempt to reduce the amount of dirt and debris that enters the housings and ductwork. However, even with a screen in place, dirt and debris still enter the blower housing. It is desirable to further reduce the amount of dirt and debris in the air that is drawn through the filter to extend the life of the filter.